Catalyst efficiency for supported metallocene catalyst

ABSTRACT

The invention provides a polymerization process with improved catalyst activity of a metallocene catalyst supported on silica treated with MAO, a process for supporting a metallocene compound on silica treated with MAO, a metallocene catalyst supported on silica treated with MAO within a certain temperature range and a process for making a metallocene catalyst supported on silica treated with MAO. The invention includes supporting the metallocene compound on a MAO-treated silica at a temperature of below 0° C. The supported catalyst is activated with an aluminum alkyl. The catalyst may be prepolymerized in a tubular reactor prior to being introduced into the polymerization reaction zone.

This is a divisional application of application Ser. No. 08/772,667,filed Dec. 20, 1996, issued Oct. 19, 1999, as U.S. Pat. No. 5,968,864.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to method of making a catalyst component. Ametallocene compound is supported on a silica material treated with analumoxane co-catalyst and complexed with the alumoxane. The supportedmetallocene catalyst may be used in the polymerization of olefins, suchas propylene. The temperature of the process for supporting themetallocene on the silica affects catalyst efficiency.

2. Description of the Prior Art

Metallocene catalysts for the polymerization of olefins are known in theart and have been known at least since U.S. Pat. No. 4,542,199, whichdescribed use of a catalyst to produce polyethylene. Since that time,patents have issued relating to isospecific and syndiospecificmetallocene catalysts. Examples of these patents include U.S. Pat. Nos.4,794,096 and 4,892,851, respectively, the disclosures of which,together with the disclosure of U.S. Pat. No. 4,542,199, are herebyincorporated by reference.

These patents disclose metallocene catalysts that are basically acomplex derived from a cyclopentadiene, i.e., a metal derivative ofcyclopentadiene, which has been ionized by an ionizing agent to form anactive cationic metallocene catalyst. It has also become known in theart that metallocenes may be supported on an inert non-reactivematerial.

In U.S. Pat. No. 5,106,804 a zirconocene is supported on magnesiumdichloride. The contact between the metallocene, the solid support andan organoaluminum compound at a temperature from 0° C. to the boilingtemperature of the hydrocarbon solvent employed in the solutions and ispreferably from 0° C. to 110° C. This patent states that in a two stepprocess of contacting the solid support with the organoaluminum and thencontacting the solid support with the metallocene, the temperature ofthe first step may be different than that of latter.

In U.S. Pat. No. 5,126,301 a fine particle carrier was treated with ametallocene and an aluminoxane, either consecutively or simultaneously.The preferred process was to treat the carrier first with themetallocene, then the aluminoxane. The temperature at which treatmentwith a solution of the metallocene occurred was −50° C. to 110° C., andpreferably from 0° C. to 80° C.

In U.S. Pat. No. 5,183,867 a metallocene, an alumoxane and anonmetallocene containing transition metal compound are reacted on asupport at a temperature from 0° C. to 100° C. In the working examplesthe catalysts were made at 25° C. and 80° C.

In U.S. Pat. No. 5,281,679 an alumoxane is deposited on a hydratedsilica gel by a reaction between the water and an aluminum trialkyl. Ametallocene is then complexed with the alumoxane is a slurry at ambienttemperature or at an elevated temperature of about 75° C.

In U.S. Pat. No. 5,296,565 a particulate carrier, an organoaluminum oxycompound, a metallocene and, optionally, an organoaluminum compound aremixed and contacted to form a supported carrier. The temperature atwhich the mix/contact takes place is −100 to 200° C., preferably −70 to100° C. A range of −30 to 200° C. is given for mixing and contacting thecarrier and the organoaluminum oxy compound is given but no range isgiven for mixing the metallocene. In the working examples mixing andcontacting the metallocene occurred at 30° C. and room temperature.

In U. S. Pat. No. 5,397,757 a metallocene complex, carbon tetrachlorideor carbon tetrabromide, an organomagnesium compound andtrimethylaluminum were combined to avoid use of aluminoxane to activatethe catalyst. The metallocene was supported on silica by slurrying at20-60° C., preferably 30-55° C.

In U. S. Pat. No. 5,529,965 a catalyst having a metallocene componentand a non-metallocene component on silica containing water and anorganometallic compound, such as trimethyl aluminum, was used topolymerize ethylene. In the working examples the catalytic componentswere supported on the silica at 165° F. (74° C.).

SUMMARY OF THE INVENTION

The invention provides a process for making a metallocene catalystuseful in the polymerization of olefins, particularly propylene. Oneembodiment of the present invention includes forming a supportedmetallocene catalyst on an inert, non-reactive support, such as silicawhich has been treated with an alumoxane. The supported metallocenecatalyst can be suspended in an inert liquid carrier, such as mineraloil, contacted with a trialkylaluminum co-catalyst, such as tri-isobutylaluminum or triethyl aluminum, and introduced into a polymerizationreaction zone which contains a monomer.

The catalyst can be pre-polymerized with the co-catalyst and an olefinmonomer. The olefin is added after the catalyst has contacted theco-catalyst. The catalyst is contacted with the co-catalyst, for acertain period of time. The catalyst and co-catalyst can be suspended inan inert liquid carrier, such as mineral oil. The prepolymerizedcatalyst is then introduced into the reaction zone. It is preferred tohave a stream of olefin contact the catalyst and co-catalyst and carrythe catalyst into the reaction zone.

In the pre-polymerization step, the catalyst may be coated with apolymer product such that the weight ratio of polymer/catalyst isapproximately 0.01-3.0. Preferably, the ratio of coating the catalyst isgreater than 1.0 and, more preferably, 2.0-3.0. The preferred olefin ispropylene.

The preferred catalyst is a metallocene catalyst of the general formula:

R″_(b)(C₅R_(5-b))(C₅R′_(5-b))MR*_(v-2)

where R″ is a bridge imparting stereorigidity to the structure to themetallocene by connecting the two cyclopentadienyl rings, b is 1 or 0indicating whether the bridge is present or not, C₅ is acyclopentadienyl ring, R and R′ are substituents on the cyclopentadienylrings and can be a hydride or a hydrocarbyl from 1-9 carbon atoms, eachR and R′ being the same or different, M is a Group 3, 4, 5 or 6 metal,R* is a hydride, a halogen or a hydrocarbyl from 1-20 carbon atoms, v isthe valence of M. The preferred co-catalyst for all supportedmetallocene catalysts is an alkylaluminum compound, and most preferablytri-isobutyl aluminum.

Improved catalytic activity is realized for isospecific, syndiospecificand aspecific metallocene catalysts as the temperature of the processfor supporting the metallocene on the MAO-treated silica decreases,i.e., the lower temperature of the supporting process, the higher thecatalyst activity.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawing wherein:

FIG. 1 is a graphic representation of the effect on catalyst activity oftemperature during the process of supporting a metallocene compound onMAO-treated silica to form an isospecific catalyst (Examples 5-12).

FIG. 2 is a graphic representation of the effect on catalyst activity oftemperature during the process of supporting a metallocene compound onMAO-treated silica to form a syndiospecific catalyst (Examples 1-4).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for synthesis of a metallocenecatalyst useful in the polymerization of α-olefins. The invention isparticularly adapted for the polymerization of propylene. The inventionincludes contacting the supported metallocene catalyst with an aluminumalkyl co-catalyst. Prepolymerizing the catalyst prior to introducing itinto a polymerization reaction zone is preferred. One embodiment of theinvention includes contacting the supported metallocene catalyst withthe aluminum alkyl co-catalyst for a certain period of time which mayvary depending on whether the catalyst is isospecific or syndiospecific.

Metallocene catalysts can be generally defined as a metal derivative ofcyclopentadiene, which has been ionized to form an active cationicmetallocene catalyst. The metallocene compound generally contains twocyclopentadienyl rings, substituted or unsubstituted, and is of thegeneral formula:

R″_(b)(C₅R_(5-b)) (C₅R′_(5-b))MR*_(v-2)

where R″ is a bridge imparting stereorigidity to the structure to themetallocene by connecting the two cyclopentadienyl rings, b is 1 or 0indicating whether the bridge is present or not, C₅ is acyclopentadienyl ring, R and R′ are substituents on the cyclopentadienylrings and can be a hydride or a hydrocarbyl from 1-9 carbon atoms, eachR and R′ being the same or different and (C₅R_(5-b)) and (C₅R′_(5-b))being the same or different, M is a Group 3, 4, 5 or 6 metal, preferablya Group IVB metal, more preferably titanium, zirconium or hafnium, andmost preferably zirconium; R* is a hydride, a halogen or a hydrocarbylfrom 1-20 carbon atoms, v is the valence of M.

R″ is a bivalent radical which bond or coordinates with (C₅R_(5-b)) and(C₅R′_(5-b)). R″ is preferably a substituted or unsubstituted alkylradical having 1-4 carbon atoms as the bridging component andsubstituents of hydrocarbyl radicals having 1-10 carbon atoms or aradical containing silicon, germanium, phosphorus, nitrogen, boron oraluminum atoms as the bridging component and substituents of hydrocarbylradicals having 1-10 carbon atoms. More preferably, R″ is preferably ahydrocarbyl or hydrosilyl radical having one atom of carbon or siliconto form the bridge. R″ may be a methylidene, ethylidene, isopropylidene,diphenylmethylidene or dimethylsilylidene radical and, most preferably,is an isopropylidene or dimethylsilylidene radical.

For an isospecific catalyst, each (C₅R_(5-b)) and (C₅R′_(5-b)) arepreferably the same and, more preferably, are a cyclopentadienyl orindenyl ring, substituted or unsubstituted. Examples of theseisospecific catalysts are dimethylsilylbis(2-methylindenyl) zirconiumdichloride and dimethylsilylbis(2-methyl-4-phenyl indenyl)zirconiumdichloride. In the alternative, for an isospecific catalyst (C₅R′_(5-b))is a sterically different substituted cyclopentadienyl ring than(C₅R′_(5-b)) in which one cyclopentadienyl ring is an unsubstitutedfluorenyl and one and only one of the distal positions of the othercyclopentadienyl rings has a bulky group as a substituent having aspatial displacement greater than a methyl (CH₃) group and, morepreferably, having a spatial displacement equal to or greater than at-butyl group (CH₃CH₃CH₃C) group as disclosed in U.S. Pat. No.5,416,228, issued May 16, 1995, hereby incorporated by reference. Anexample of this isospecific catalyst isisopropylidene(t-butylcyclopentadienyl-1-fluorenyl)zirconium dichloride.

For a syndiospecific catalyst, each (C₅R_(5-b)) and (C₅R′_(5-b)) aredifferent and bilateral symmetry exists at least for (C₅R_(5-b)) andpreferably for both (C₅R_(5-b)) and (C₅R′_(5-b)). Preferably,(C₅R_(5-b)) is an unsubstituted cyclopentadienyl or cyclopentadienylsubstituted in proximal positions and (C₅R′_(5-b)) is fluorenyl,substituted or unsubstituted. Bilateral symmetry is defined as thecondition in which there are no substituents or one or more substituentson one side and no substituents or one or more of the same substituentson the other side in the same relative position such that a mirror imageis formed from one side to another. One example of such a compound isisopropylidene(cyclopentadienyl-1-fluorenyl)zirconium dichloride,abbreviated iPr(Cp)(Flu)ZrCl₂. Bilateral symmetry is illustrated by aplane bisecting the bridge resulting in the right side of each ligandbeing a mirror image of its left side. An illustration of the ligands ofthis compound are shown below:

Pseudobilateral symmetry is defined as symmetry such that a mirror imageexists from one side to the other in regard to the existence andposition of substituents but the substituents themselves are notidentical. Pseudobilateral symmetry is illustrated by a plane bisectingthe ligand with the substituents being in the same relative position oneach side of the plane, i.e., forming a mirror image as to location ofsubstituents on the substituted cyclopentadienyl ring, but thesubstituents are not the same. This is illustrated below:

The metallocene compounds described above are supported to make aheterogeneous or solid catalyst. The support can be any solid which ischemically inert and unreactive with the metallocene and the othercatalyst components. Examples of support material are porous materialssuch as talc; inorganic oxides, such as Group IIA, IIIA, IVA or IVBmetal oxides, specifically, silica, alumina, magnesia, titania,zirconia, and mixtures thereof; and resinous materials, such aspolyolefins, specifically, finely divided polyethylene, as disclosed inU.S. Pat. No. 4,701,432, hereby incorporated by reference. The supportis preferably silica having high surface area in a range from 200 m²/gto 800 m²/g and small average pore volume in a range from 0.70 ml/g to1.6 ml/g. One example of silica operative in this invention ischromatography grade silica. The preferred silicas are sold under thetradenames Ashi Olin H-121, Fuji Silicia P10, Q-6 and G-6.

The silica was treated with methylalumoxane (MAO) in the followingmanner: The silica had water removed to a level of approximately 0.5%.The dried silica was slurried in a nonpolar solvent. A solution ofalumoxane in solvent was added to the silica slurry. After heating andsubsequently cooling the slurry, the solid (silica treated withalumoxane) was separated out and (optionally) dried.

The metallocene was contacted with the MAO-treated silica to form asupported metallocene catalyst in the following manner: A solution ofmetallocene in a hydrocarbon solvent was added to a slurry of silicatreated with alumoxane also in a hydrocarbon solvent, preferably thesame solvent as the metallocene solution and maintained while stirringat a set temperature for thirty minutes to seventy-two hours. The solid,metallocene supported on silica treated with alumoxane, was separatedout and dried. The MAO/silica weight ratio is between 0.5:1 to 3:1 whilethe per cent metallocene is between 1.0%-4.0%.

A suspension was formed with the supported metallocene catalyst in aninert liquid carrier, such as mineral oil. The liquid carrier isselected based on the following properties:

1. The liquid does not dissolve the solid catalyst component.

2. The liquid has minimal chemical interaction with the catalystcomponent.

3. The liquid is preferably an inert hydrocarbon.

4. The liquid only “wets” the catalyst component

5. The liquid has sufficient viscosity to maintain the catalystcomponent in suspension without excessive agitation. Liquids which wouldbe effective in this invention would be long chain hydrocarbons, such asmineral oil and polyisobutylene. This listing is not intended to becomplete and all inclusive but is merely made to show examples of usefulliquid media.

A co-catalyst is utilized to aid in the activation of the catalyst forthe polymerization reaction. The most commonly used co-catalyst is anorganoaluminum compound which is usually an alkyl aluminum. The aluminumalkyl is of the general formula AlR′₃ where R′ is an alkyl of from 1-8carbon atoms or a halogen and R′ may be the same or different with atleast one R¹ being an alkyl. Examples of aluminum alkyls are trimethylaluminum (TMA), triethyl aluminum (TEAl), triisobutyl aluminum (TiBAl)and diethyl aluminum chloride (DEAC). The preferred co-catalysts analuminum trialkyl, specifically TEAl or TiBAl.

In order to increase the efficiency of a syndiospecific supportedmetallocene catalyst, the catalyst is pre-polymerized. Basically, thepre-polymerization reaction occurs as a monomer is introduced into amixture of catalyst and co-catalyst. A small amount of the monomer ispolymerized, and in so doing, it adheres to the surface of the catalystand forms a coating. Any known method for prepolymerizing a catalyst canbe used for the catalyst of the present invention.

In pre-polymerizing the catalyst, a weight ratio of polymer/catalyst ofapproximately 0.01-3.0 is desirable. Preferably, the weight ratio ofpolymer to catalyst is less than 1.0, more preferably less than 0.5.

According to one embodiment of the invention, the supported metallocenecatalyst is contacted with a co-catalyst and then is prepolymerized bycontact with the monomer prior to being introduced into a polymerizationreaction zone which contains additional monomer. In a preferredembodiment, the contact of the catalyst with the co-catalyst occurs in aholding tank in which the catalyst/co-catalyst mixture is allowed toage. The catalyst/co-catalyst mixture may be fed into the reactor in acontinuous or periodic manner.

The contact of the catalyst/co-catalyst mixture with the monomer forprepolymerization can take place in a pipe which carries the catalystinto the polymerization zone. The contact time or residence time of thecatalyst in the pipe need be only a few seconds. A minimum of threeseconds of pre-contact between the catalyst/co-catalyst and the monomeris sufficient to significantly increase the efficiency of asyndiospecific catalyst. For an isospecific catalyst the minimumpre-contact time is 1-2 seconds. The concentration of co-catalyst in thestream may be varied as the co-catalyst is transferred into thepolymerization reaction zone. A preferred concentration would be lessthan 10% co-catalyst in the stream by weight. All of the co-catalystnecessary for the polymerization reaction in the reaction zone need notbe fed through this contact pipe. A portion of the desired amount ofco-catalyst in the reactor may be added directly to the reaction zone.

The invention concerns an improvement in catalyst efficiency realized bycontrol of the temperature during the process of contacting themetallocene compound with the MAO-treated silica. Decreased temperatureof the process for supporting the metallocene on the MAO-treated silicaresults in higher the catalyst activity. Catalyst efficiency improvedwhen the temperature was at below room temperature (25° C.). Thepreferred temperature range for supporting the metallocene compounds onthe MAO-treated silica is from at or below room or ambient temperature(25° C.) down to −50° C. It is more preferred that the temperature be 0°C. or lower. It is most preferred that the temperature range be from 0°C. down to −20° C.

The invention having been generally described, the following examplesare given as particular embodiments of the invention and to demonstratethe practice and advantages thereof. It is understood that the examplesare given by way of illustration and are not intended to limit thespecification or the claims to follow in any manner.

Preparation of the Metallocene

A manipulations were carried out under argon using standard Schlenktechniques unless otherwise noted.

SYNDIOSPECIFIC

Preparation of the ligand [Ph₂C(Flu-Cp)]

To a solution of 50 g fluorene in 200 ml anhydrous tetrahydrofuran atroom temperature was added dropwise at 0° C., 207 ml of a 1.6 molarsolution of n-butyllithium in hexane. The reaction mixture was stirredfor 1 h at room temperature and cooled to −78° C. upon which light brownsolid precipitated. 69.3 g of diphenylfulvene was then added to thereaction mixture. The heterogeneous mixture was allowed to graduallycome to room temperature with constant stirring and was stirred at roomtemperature overnight (˜18 h). The reaction mixture was cooled to 0° C.and cautiously quenched with dilute hydrochloric acid (10 to 18%)(slightly exothermic). The mixture was stirred at 0° C. for 5 minutesand diluted with 300 ml water and 200 ml hexane and filtered through amedium frit funnel. The resulting solid was washed with water (500 ml)followed by hexane (300 ml). The resulting wet solid was air driedfollowed by drying under vacuum with slight warming. To completelyremove entrapped solvent the sample was heated at 100° C. under highvacuum overnight. The yield of THF-free and water-free ligand was in therange 70-80%.

Preparation of the metallocene [Ph₂C(Flu-Cp)ZrCl₂]

A three-necked 3L flask equipped with mechanical stirrer and pressureequalized addition funnel was charged with 73.2 g of rigorously driedligand obtained from the previous method (It should be noted that, theligand must be dry but not necessarily free of THF. In case, THF-freeligand is used, it appears that it may be advantageous to use excess ofn-butyllithium to complete dianion formation). One liter of anhydrousether was added and the stirring initiated. The slurry was cooled to 0°C., and 254.2 ml of 1.6 molar n-butylithium in hexane was added dropwisecautiously. The temperature of the reaction mixture was graduallyallowed to come to room temperature and stirred overnight (˜18 h). Thestirring was stopped and the solid was allowed to settle. Thesupernatant was decanted. The resulting solid was washed with twoportions of anhydrous hexane (2×500 ml). A fresh batch of 1.0 L ofanhydrous hexane was added and the stirring was initiated. The reactionmixture was cooled to 0° C. and 42 g of ZrCl₄ was added in smallportions. The temperature was allowed to come to room temperature andstirred overnight (18 h). The stirring was stopped and the solid allowedto settle. The supernatant was decanted and the solid dried undervacuum. Total weight, 112 g (contains LiCl).

Chloroform Extraction Method

112 g of the crude product was added to a 3L, 3 neck-flask and 2 Lamylene-free chloroform (amylene present as a preservative in chloroformwas removed either by purging with argon for 20 min or by removal undervacuum for a few minutes followed by release of vacuum with argon andrepetition of the process 3-4 times) was added. The mixture wasmagnetically stirred at room temperature for 45 min; the stirringstopped and the flask was placed in a warm water bath. The solidsuspension was allowed to settle. Using a cannula, the supernatant wasfiltered through a fritted funnel packed (⅔ full) with glasswool. Afterthe filtration was complete the remaining solid was rinsed withadditional CHCl₃ (or until the undissolved solid is pale colored) andthe washings were filtered into the receiving flask. The solvent wasremoved from the filtrate and the resulting bright red solid, 101 g(>95% of theoretical recovery), was stored in the drybox.

ISOSPECIFIC

Preparation of the ligand [Me₂Si(2-MeInd)₂]

The synthetic procedure reported for 2-methylindene in J. Org. Chem. 47,1058 (1982) was followed to obtain the compound as a colorless oil afterdistillation.

To a solution of 2-methylindene (2.58 g) in dry diethylether (150 ml), asolution of methyllithium in ether (1.4M, 14 ml) was added slowly atroom temperature and stirred overnight. The solvents were removed underreduced pressure and the resulting solid was slurried in dry hexane (150ml). Dichlorodimethylsilane diluted in ether (30 ml) was transferredinto the previous solution which was prechilled to −78° C. The reactionmixture was allowed to come to room temperature and stirring continuedovernight. The reaction mixture was filtered and the solvents wereremoved from the filtrate under reduced pressure to obtain a whitesolid. The solid was washed with a small amount of hexane which wasprechilled to −78° C. to obtain a whiter powder (0.75 g). From thehexane wash a second crop of the ligand was obtained (0.25 g). Totalyield was 32%.

Preparation of the metallocene [Me₂Si[2-MeInd]₂ZrCl₂]

The ligand (1.0 g) obtained from the previous procedure was dissolved inanhydrous tetrahydrofuran (40 ml) and a solution of n-butyllithium inhexane (1.6M, 4.4 ml) was and stirred for 3 hours. The solvents wereremoved under vacuum to obtain a off-white solid which was washed withdry hexane under nitrogen atmosphere. The solid was cooled to −78° C.and methylene chloride prechilled to −78° C. was added followed by aslurry of zirconium tetrachloride in methylene chloride which was alsoprechilled to −78° C. The reaction mixture was allowed to gradually cometo room temperature and stirred overnight. The solution was filtered andthe solid was washed with hexane. The hexane washings were added to thefiltrate at which time a off-white solid precipitated. Upon filtrationthe filtrate was concentrated and cooled to −78° C. for several hours toobtain a yellow solid. This yellow solid (0.30 g) was isolated byfiltration and was found to be a mixture (65:35) or rac- andmeso-isomers by NMR spectroscopy. ¹HNMR (CD₂Cl₂) (in ppm), 7.67(2d),7.45(d), 7.08(t), 6.99(t), 6.76(s), 6.74(s), 6.64(s), 2.44(s), 2.20(s),1.42(s), 1.29(s), 1.22(s).

20 g of silica (P-10, average particle size 25 microns) was used asreceived. Toluene (200 mL) was added and the slurry stirred at roomtemperature. The MAO solution (3×500 mL) was then added to the silicaslurry. The slurry was then heated to reflux for 4 hours. After coolingto room temperature, the supernatant was decanted by cannula and thesolid washed four times each with 500 mL portions of toluene. The solidwas then washed three times each with 100 Ml of hexane and then dried at45° C. for 1 hour in vacuo. The MAO/silica weight ration in the isolatedproduct was 0.9.

Supporting of Metallocene and MAO-Treated Silica

A toluene solution (25 mL) of metallocene (0.1 g) was added via cannulato a stirred slurry of MAO/SiO₂ (5 grams) in toluene (75 mL). Uponcontact with the MAO/SiO₂, the red metallocene turns the solid deeppurple. The slurry was stirred for one hour at the temperatures in thetable below. The supernatant liquid was decanted and the solid washedthree times each with 75 mL hexane. The purple solid was then driedovernight in vacuo at room temperature.

The following Examples illustrate the present invention in more detailand the advantages to be gained in increased catalyst efficiency byintroducing a catalyst prepared with a low temperature supportingprocess into a polymerization reaction zone.

EXAMPLE I

The catalyst was prepared per the procedure above. The temperature atwhich the slurry of the syndiospecific metallocene and MAO-treatedsilica was stirred was 0° C.

A slurry of 50 mg solid catalyst component and 150 mg oftriisobutylaluminum (TIBAl) was prepared in 1.5 ml mineral oil. all ofthe slurry suspension was added to a 4.0 liter autoclave from which theair had been sufficiently replaced by nitrogen. The autoclave was thencharged with 2.9 liters of liquid propylene and 16 mmoles of gaseoushydrogen. The mixture was then heated to 60° C. and maintained for 60minutes. The polymer was then dried at 80° C. Polymerization results areshown in Table 1.

Polymerization Reagents Conditions Catalyst: 50 mg Temperature: 60° C.TIBAl: 150 mg 25% solution in hexane Time: 1 hour Propylene: 2.9 L (0.72kg) Hydrogen: 16 mmol

EXAMPLE II

The same procedure as Example I was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 25°C. Polymerization results are shown in Table 1.

EXAMPLE III

The same procedure as Example I was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 60°C. Polymerization results are shown in Table 1.

EXAMPLE IV

The same procedure as Example I was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 80°C. Polymerization results are shown in Table 1.

EXAMPLE V

The same procedure as Example I was used except the metallocene compoundwas dimethylsilylbis(2-methylindenyl) zirconium dichloride and thetemperature at which the slurry of the metallocene and MAO-treatedsilica was stirred was −20° C. and the alkylaluminum used wastriethylaluminum. Polymerization results are shown in Table 1.

EXAMPLE VI

The same procedure as Example V was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 0°C. Polymerization results are shown in Table 1.

EXAMPLE VII

The same procedure as Example VI was used except the silica used had anaverage particle size of 15 microns. Polymerization results are shown inTable 1.

EXAMPLE VIII

The same procedure as Example V was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 25°C. Polymerization results are shown in Table 1.

EXAMPLE IX

The same procedure as Example V was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 60°C. Polymerization results are shown in Table 1.

EXAMPLE X

The same procedure as Example IX was used except the silica used had anaverage particle size of 15 microns. Polymerization results are shown inTable 1.

EXAMPLE XI

The same procedure as Example V was used except the temperature at whichthe slurry of the metallocene and MAO-treated silica was stirred was 80°C. Polymerization results are shown in Table 1.

EXAMPLE XII

The same procedure as Example XI was used except the silica used had anaverage particle size of 15 microns. Polymerization results are shown inTable 1.

TABLE 1 Temp. Yield Example Al Alkyl (° C.) Silica (g) Efficiency 1TiBAl 0 P-10 322 6440 (25 μm) 2 TiBAl 25 P-10 270 5400 (25 μm) 3 TiBAl60 P-10 189 3780 (25 μm) 4 TiBAl 80 P-10 132 2640 (25 μm) 5 TEAl −20 G-6905 12569 (38 μm) 6 TEAl 0 G-6 786 10917 (38 μm) 7 TEAl 0 P-10 780 10833(15 μm) 8 TEAl 25 G-6 486 9720 (38 μm) 9 TEAl 60 G-6 673 9347 (38 μm) 10TEAl 60 P-10 700 9122 (15 μm) 11 TEAl 80 G-6 694 9639 (38 μm) 12 TEAl 80P-10 512 7111 (15 μm)

Catalyst efficiency is related to temperature of the process ofsupporting the metallocene on the MAO treated silica. Catalystefficiency improved when the temperature was lower. Catalyst efficiencywas highest when the temperature was at 0° C. or below down to −20° C.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letter of Patent of the United States of America is:
 1. A metallocene catalyst supported on an alumoxane-treated silica comprising: a) a metallocene compound of the general formula R″_(b)(C₅R_(b-5)) (C₅′R′_(b-5))MR*_(v-2) where R″ is a bridge imparting stereorigidity to the structure to the metallocene by connecting the two cyclopentadienyl rings, b is 1 or 0 indicating whether the bridge is present or not, C₅ is a cyclopentadienyl ring, R and R′ are substituents on the cyclopentadienyl rings and are a hydride or a hydrocarbyl from 1-9 carbon atoms, each R and R′ being the same or different, M is a Group 3, 4, 5 or 6 metal, R* is a hydride, a halogen or a hydrocarbyl from 1-20 carbon atoms, v is the valence of M; b) an alumoxane-treated silica; wherein the metallocene compound has been supported on the alumoxane-treated silica at a temperature maintained in the range of −20° C. to 0° C. during the course of the reaction between a) and b).
 2. The catalyst as recited in claim 1 wherein the metallocene is a stereospecific catalyst precursor.
 3. The catalyst as recited in claim 2 wherein the metallocene is an isospecific catalyst precursor.
 4. The catalyst as recited in claim 2 wherein the metallocene is an syndiospecific catalyst precursor.
 5. The catalyst as recited in claim 1 wherein each (C₅R′₄) ligand is different and bilateral symmetry exists for (C₅R₄) as to a perpendicular plane bisecting the (C₅R₄) ligand.
 6. The catalyst as recited in claim 5 wherein (C₅R′₄) is a fluorenyl ring, substituted or unsubstituted.
 7. The catalyst as recited in claim 5 wherein (C₅R₄) is an unsubstituted cyclopentadienyl ring.
 8. The catalyst as recited in claim 1 wherein the metallocene is isopropylidene(cyclopentadienyl-1-fluorenyl)zirconium dichloride.
 9. The catalyst as recited in claim 1 wherein each (C₅R₄) and (C₅R′₄) are the same.
 10. The catalyst as recited in claim 9 wherein (C₅R₄) and (C₅R′₄) are indenyl or substituted indenyl rings.
 11. The catalyst as recited in claim 10 wherein (C₅R₄) and (C₅R′₄) are (2-methylindenyl) or (2-methyl-4-phenyl indenyl).
 12. The catalyst as recited in claim 1 wherein the metallocene is dimethylsilylbis(2-methylindenyl) zirconium dichloride or dimethylsilylbis(2-methyl-4-phenyl indenyl)zirconium dichloride.
 13. The catalyst as recited in claim 1 wherein the metallocene is isopropylidene(t-butylcyclopentadienyl-1-fluorenyl)zirconium dichloride.
 14. The catalyst as recited in claim 1 wherein the silica has surface area in a range from 200 m²/g to 800 m²/g and average pore volume in a range from 0.70 ml/g to 1.6 ml/g.
 15. The catalyst as recited in claim 1 wherein the silica has an average particle size in a range from 15 to 38 microns.
 16. The catalyst as recited in claim 15 wherein the silica has an average particle size of 25 microns.
 17. The catalyst as recited in claim 15 wherein the silica has an average particle size of 38 microns.
 18. The catalyst as recited in claim 15 wherein the silica has an average particle size of 15 microns. 